Hithertobefore, different kinds of compounds having the differentiation-inducing activity have been studied. A method of making decarcinogenesis of the tumor cells by inducing the differentiation of the tumor cells has been proposed as described, for instance, in the "Proc. Natl. Acad. Sci. USA" 77, page 2936 (1980); the "J. Med. Chem." 25, page 1269 (1982); the "Blood" 62, page 709 (1983) and "THE RECINOIDS" Vol. 1-2, M. B. Sporn et al, Academic Press (1984). Further, for example, Japanese patent application first application "Kokai" No. 163387/82 (or its corresponding U.S. Pat. No. 4,542,219) discloses some ethylene glycol derivatives; Japanese patent application first publication "Kokai" No. 199820/85 discloses a substance OC-1 which is extracted from an earth worm, Oliochaeta; and Japanese patent application first publication "Kokai" No. 76440/86 discloses some derivatives of benzoic acid, and the respective compounds as disclosed in the afore-said three Japanese patent application first publications are all such antitumor compounds having the differentiation-inducing activities which stimulate the differentiation of the tumor cell and thus invoke the decarcinogenesis of the tumor cells.
We, the present inventors, have now made our investigations in an attempt to provide new compounds which have the differentiation-inducing activity, and to provide these new compounds as an antitumor agent.